A method of measuring the distance to a target object by utilizing sound waves by a distance measuring device including a speaker and a microphone exists (refer to NPL 1 for example). In this method, a reflected wave caused by reflection of a sound wave (output wave), which has been emitted from the speaker, by the target object is received by the microphone. Then, the distance from the distance measuring device to the target object is measured by identifying the time required until the sound wave emitted from the speaker is reflected and reaches the microphone. This method can be realized if the distance measuring device includes the speaker and the microphone. Thus, it is also possible to utilize a smartphone, a tablet, or the like that is commonly prevalent as the distance measuring device for example.